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Sometimes people mistake symptoms of stomach flu, or gastroenteritis, for the viral infection we commonly call "flu." But the "stomach flu" is not the flu. It is a gastrointestinal illness that can be caused by a number of factors including bacteria, viruses and parasites. The flu, which causes fever, congestion, muscle aches, and fatigue, is caused by viruses only.

How Does Stomach Flu Differ From Influenza?

Stomach flu actually refers to gastroenteritis or irritation and inflammation of the stomach and intestines (the gastrointestinal tract). Gastroenteritis may be caused by a virus, bacteria, parasites in spoiled food or unclean water, or another trigger such as lactose intolerance, which is caused by a reaction to dairy products.

Influenza (flu), on the other hand, is a viral infection that mimics a cold except that it starts forcefully with symptoms of fatigue, fever, and respiratory congestion. While more than 100 different virus types can cause a common cold, only influenza virus types A, B, and C cause flu. More severe cases of influenza can lead to life-threatening illnesses such as pneumonia.

In addition, while antibiotics can treat a bacterial infection that may cause gastroenteritis, antibiotics cannot treat influenza because flu is caused by a virus.

You can avoid dehydration by continuing to drink fluids. When you are able to keep food down, bland foods -- like toast, rice, bananas, and applesauce -- should be tried first. However, experts now recommend returning to a normal diet within 24 hours, if possible.

What Causes a Stomach Flu?

There are many causes of gastroenteritis, including bacteria, viruses, parasites, dairy products, and poor hygiene.